1. Field of the Invention
This invention relates to electric heaters, and more particularly to such heaters utilizing support insulators for retaining and securing electric heater coils therein.
2. Description of the Prior Art
Electric heaters, utilizing resistance wire supported in a frame are known in the art. Such heaters, typically called open-coil heaters, require the use of insulators to separate the resistance wire from the frame structure and to avoid the possibility of a short circuit between the resistance wire and the frame. Heaters of this type similarly require the use of means for retaining the resistance wire in a predetermined, desired configuration with respect to the frame.
Prior art devices are known which attempt to provide insulators including coil holders for retaining a heater coil and insulating the same from the heater framework. Wightman et al., U.S. Pat. No. 3,846,619 discloses the use of insulator means mounted on cross beams of a heater frame for supporting a helical heater wire. Clip means are required to be attached to the insulators, however, in order to properly support the heater coil. The clips need to be specially formed with flange surfaces bent in non-planar configurations to retain the heater wire. Moreover, insertion of a convolution of the coil within the clip is made difficult, and removal of the coil, which might be required for maintenance or repair, is extremely difficult. The cross beams of the framework require a particular structure, and incorporate tabs to interact with portions of the insulator body to retain the insulator therein. Similarly, tabs are required on the clip means to secure the same on the insulators. In summary, a structure is disclosed in the reference, requiring a number of complicated steps eliminated by the present invention. Specifically, the presently disclosed structure embodies a unified insulator support which may be easily mounted in the cross beams of a frame. The mounting process utilizes a first set of notches in the insulator structure, while the coil is secured by a second set of notches. Tabs are not required, and assembly of the device is simplified.
Simmons, U.S. Pat. No. 1,698,282, similarly discloses an electric heater incorporating insulators, or supports, which require special manipulation for mounting on the cross beams. Additionally, each support structure requires the use of two insulator elements. Simultaneous manipulation of the two elements is required in a 90.degree. rotation for mounting the support structure, and a complicated manipulation of several combined support structures is required for the removal of a single damaged support. Moreover, the use of cotter pins is mandated in order to secure the supports against displacement. Unlike the Wightman et al. disclosure, the supports in Simmons cannot protrude through the cross beams, and thus may support a heater coil on only one side of the frame.
Hartman, U.S. Pat. No. 2,856,500, discloses a single integral insulator for an electrical heater which is mounted to a reflector in the heater. The reflector includes a plurality of key openings for receiving key-like projections from the insulator. The projections are narrower than the body of the insulator, and disposed on opposite sides of the body with respect to the heater coil support means. Accordingly, the possibility of providing a single support structure capable of supporting electric wire on both sides of a support beam is precluded by the disclosed structure. As in Wightman et al., tabs are required to be manufactured in the support beams for the insulators, and as in Simmons, special rotational steps are needed for mounting the insulators on the heater reflector.
Other teachings of insulators and spacers used in conjunction with electric heaters include McKeown U.S. Pat. No. 2,177,930; Gasparaitis, U.S. Pat. No. 3,632,981 and Laing, U.S. Pat. No. 3,218,437. Weimar, U.S. Pat. No. 1,712,860 discloses the use of two insulators above and below a cross arm of a telephone, electric or telegraph pole, the insulators having an annular groove for the wire.
It is accordingly seen that none of the prior art references disclose, either singly or in combination, an easily fabricated, easily assembled and simplified structure for supporting resistance wire in electric heaters. The present invention provides an insulated supporter, for an electric heater, which is integrally formed and is substantially symmetric. These features permit insertion of the insulator within the support beam structure of an electric heater with a terminal orienting and aligning effort, and further permit straightforward assembly of the heater wire to the frame by simplified attachment to the insulator.
Mounting of the insulators to the support beams is accomplished by insertion into a cavity, a snapping or clipping action taking place between the beam structure and notches on the insulators. A second set of notches provides a similar snap-fit for the resistance heater wire mounted on the support insulators.